1. Field of the Invention
The present invention relates to a device for driving a plurality of sector blades which serves as a lens shutter or an iris diaphragm of a camera.
2. Description of the Related Art
In a typical sector blade driving devices of a camera such as lens shutters and iris diaphragms, a plurality of sector blades (shutter blades or diaphragm blades) are driven to change the size (diameter) of a continuously adjustable photographic aperture (lens aperture) formed at the center of the plurality of sector blades. Such sector blade driving devices generally have a fixed photographic aperture, a plurality of sector blades and a cylindrical portion which surrounds the sector blades. The sector blades enter or retreat from an optical path defined by the fixed photographic aperture to change the size of the photographic aperture (the adjustable photographic aperture) of the sector blade driving device, while the cylindrical portion surrounds the sector blades to prevent harmful light such as stray light from coming into an optical path defined by the photographic aperture of the sector blade driving device.
In such conventional sector blade driving devices, there must be a radial clearance between the inner peripheral surface of the cylindrical portion and the radially outermost position in the range of movement of each sector blade to prevent each sector blade from bumping against the inner peripheral surface of the cylindrical portion. Such a radial clearance is a leading cause of an increase in size of the sector blade driving device.
The present invention has been devised in view of the problem noted above, and accordingly provides a compact sector blade driving device, and in particular, provides a small diameter.
For example, a sector blade driving device is provided, including a plurality of sector blades which define an adjustable photographic aperture; a cylindrical member which surrounds the periphery of the sector blades to prevent harmful light from entering the photographic aperture from outside of the sector blade driving device; resilient contact-portions which form a part of the cylindrical member, each of the resilient contact-portions corresponding to each the sector blades. The sector blades are in contact with the resilient contact-portions when the sector blades are fully opened.
The cylindrical member can include a cylindrical body having openings in which each outer peripheral portion of the sector blades can enter, respectively, when the sector blades are fully opened; and resilient sheets attached to the cylindrical body so as to cover the openings, respectively, so that each the sector blades is in contact with each the resilient sheets through the openings when the sector blades are fully opened.
One of opposite ends, of each of the resilient sheets, which extends in a circumferential direction of the cylindrical member can be secured to an outer peripheral surface of the cylindrical body, wherein the other end of each of the resilient sheets is not secured to the cylindrical member.
One of opposite ends, of each of the resilient sheets, which extends in an optical axis direction of a photographing optical system can be secured to an outer peripheral surface of the cylindrical body, wherein the other end of each of the resilient sheets is not secured to the cylindrical member.
The entire outer edge of each of the resilient sheets can be secured to an outer peripheral surface of the cylindrical body.
It is desirable for the cylindrical member to include a fixed photographic aperture positioned adjacent to the plurality of sector blades to be in alignment with the adjustable photographic aperture.
The sector blade driving device can further include a cylindrical base to which the cylindrical member is fixed, wherein the plurality of sector blades being positioned between the cylindrical base and the cylindrical member.
The sector blade driving device can further include a drive ring which is supported by the cylindrical base to be rotatable in a circumferential direction of the cylindrical base, the plurality of sector blades being driven via rotation of the drive ring.
It is desirable for the cylindrical member and the cylindrical base to include a first fixed photographic aperture and a second fixed photographic aperture, respectively, the adjustable photographic aperture defined by the plurality of sector blades being positioned between the first fixed photographic aperture and the second fixed photographic aperture and in alignment with the first fixed photographic aperture and the second fixed photographic aperture in an optical axis direction of a photographing optical system.
In another embodiment, a sector blade driving device is provided, including a plurality of sector blades which defines an adjustable photographic aperture; a cylindrical member having a cylindrical wall surrounding the periphery of the sector blades, a plurality of slots being formed on the cylindrical wall so that the sector blades can partly enter the slots when fully opened, respectively; and a plurality of resilient members which cover the slots so that the sector blades are in contact with the resilient members through the slots when the sector blades are fully opened, respectively.
Each of the resilient members can be partly fixed to the cylindrical member.
The present disclosure relates to subject matter contained in Japanese Patent Application No.2001-206156 (filed on Jul. 6, 2001) which is expressly incorporated herein by reference in its entirety.